Should a mother have to spend the night in a jail cell – with no warrant, no probable cause, and no opportunity to contest her detention – just because the feds want to investigate her immigration status? We think the answer is clearly no. Wednesday the federal district court in Rhode Island agreed, issuing an important decisionin the case of Ada Morales, a U.S. citizen who has been unlawfully jailed by Rhode Island authorities on two separate occasions based on invalid immigration detainers.

Morales, who was born in Guatemala, became a naturalized U.S. citizen in 1995. Yet in May 2009, when she was arrested on state grounds, ICE issued an immigration detainer against her – a fill-in-the-blank form stating that an "investigation has been initiated" into whether she might be a non-citizen subject to deportation. The Rhode Island Department of Corrections treated that detainer as a basis to keep her in jail for a full day after a state judge ordered her released on bail. They did so even though Morales told them that she was a U.S. citizen, and offered to show them her naturalization certificate and passport to prove it.

It was only after spending the night in jail, being subjected to a humiliating strip-search, and being taken to an ICE office in a prisoner van that authorities finally confirmed that Morales is a U.S. citizen and cleared her for release. An ICE official apologized for her wrongful detention, but he acknowledged that it could happen again in the future. Morales had good reason to be concerned – in fact, she had been unlawfully jailed on an ICE detainer in virtually identical circumstances once before, in 2004. Hoping to eliminate that risk in the future and to remedy the past violations of her rights, Morales filed a lawsuit against the United States, ICE officials, and state defendants.

The district court issued a thorough decision permitting Morales's case to proceed. The court reaffirmed the basic Fourth Amendment rule that mere investigative interest – including investigation into one's immigration status – is not enough to justify warrantless imprisonment. It made clear, too, that ICE cannot subject someone to an immigration detainer simply because she was born abroad. As the court explained, "[t]o hold otherwise would mean that the approximately 17 million foreign-born United States citizens could automatically be subject to detention and deprivation of their liberty rights."

The court also recognized that immigration detainers are simply requests from the federal government – not orders – and that state and local officials can be held legally responsible if they choose to jail people on that basis without probable cause or due process, in violation of the Constitution. In fact, a growing number of states and localities have already decided that the risk is not one worth taking. Connecticut, California, Washington DC, Newark, Cook County and Chicago, New Orleans, and Miami-Dade County, to name just a few, have all adopted laws or policies in recent years limiting their entanglement with ICE detainers.

This week's decision is an early step in Morales's case, but it's an important reaffirmation of a basic American principle: No matter who you are or where you were born, you cannot be denied fundamental rights.